Twitter's logo on a computer screen in London in September 2011. / Leon Neal, AFP/Getty Images

by Matt Krantz, USA TODAY

by Matt Krantz, USA TODAY

Investors looking to buy into the much-anticipated IPO of Twitter are going to have some waiting to do before seeing if there will be any shares for them.

Details are still scarce on the initial public offering of Twitter, since the company has only provided its registration privately to the Securities and Exchange Commission. Investors are still waiting for details on how many shares of the social media company will be offered, the timing of the offering and the price of the shares.

Typically, IPOs of much-anticipated IPOs are doled out by the investment bankers running the deal to their favored clients and long-standing customers. Individual investors interested in buying shares usually have to purchase them in the open market once trading begins. But experts are thinking Twitter may likely follow the lead set by Facebook and other recent IPOs in holding back some shares for individual investors.

With most recent IPOs, there will usually be about 20% of the shares outstanding held back for individual investors, says Jay Ritter, professor of finance at the University of Florida. In Facebook's case, the number was actually higher, 25%, because demand for large institutional investors weakened as the deal neared. Many large investors were turned off by Facebook's lofty price range, the large number of shares being offered and its questionable future in mobile, and pulled back their purchases. Facebook raised more than $16 billion in the largest Internet IPO in history, Ritter says.

Investors interested in getting a piece of Twitter will need to check with their brokerages over the coming months to see how many shares, if any, will be available to them. Most large online brokerages, including TD Ameritrade, Fidelity and Charles Schwab, have deals with underwriters that allow them to get allocations to certain IPOs.

More details will be revealed after Twitter officially files its IPO registration statement for the public to see. If the deal is sold in early December, as Ritter suspects it might be, brokers will get more details of how many shares they will have in November or perhaps earlier. Interest in shares will likely be strong, especially since shares of other social networking companies have been rallying this year, Ritter says. "Twitter is definitely benefiting from the recent stock market gains of other social networking companies," he says.